


The Life of the Former UnderFell Royal Scientist

by SXH1417



Category: Undertale (Video Game)
Genre: Dadster, Depression, Fluff, Fluff and Hurt/Comfort, Gen, Good W. D. Gaster, Heavy Angst, Mentions of Suicidal Thoughts, Mentions of Violence, Sickly children, Underfell AU
Language: English
Status: Completed
Published: 2019-05-02
Updated: 2019-05-02
Packaged: 2020-02-15 22:30:10
Rating: Mature
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,617
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/18678625
Author URL: https://archiveofourown.org/users/SXH1417/pseuds/SXH1417
Summary: Gaster regretted many things in his life. He regretted making it to the underground before the barrier closed. He regretted working for the king. He regretted not doing enough to help their kind.A summary of the life and "death" of UnderFell Gaster. Not everything in his world was horrible. Not everything he did was unethical. He held regrets.





	The Life of the Former UnderFell Royal Scientist

**Author's Note:**

> Hey, guys. This story is a revamping of an idea I had before I published my first Undertale fic. This will be part of a series that's rating will change. I hope you guys enjoy!

Gaster regretted many things in his life. He regretted making it to the underground before the barrier closed. He regretted working for the king. He regretted not doing _enough_ to help their kind.

Gaster watched the world around him as it quickly deteriorated to its horrible state. He watched friends and even family turn against each other. He was there when Asgore had lost his children. He was there when Toriel, overcome with grief, fled the castle and the Capital. He tried to get her to stay. She wouldn’t listen to him, because he didn’t have children of his own… He was there when the King became recluse and refused to even look at his people.

The King turned his back on him and their kingdom. Gaster regretted not making Asgore leave his room, not forcing him to see the growing problems of the world.

This regret and guilt had him striving to make it right. He left Alphys with the DT experiments while he worked on a bigger project. He needed to fix what had happened.

He strove to recreate what the King and the Queen had lost. Through experiments that left him maimed and jittery, shaking like he had that human disease called Parkinson’s, he succeeded. He could never perform surgery again, but he taught Alphys everything he knew, so she could take his place one day. Even for a boss monster, he was getting old anyway.

That was a minor cost for the reward. The reward he got left him with nothing but long forgotten love to fill his soul. A small little soul sitting in that test tube. He could only hope that they survived.

Gaster had rushed to the castle to tell him the good news, only to find Asgore tending to the flowers. He thought it had been a good sign. Maybe Asgore was finally ready to talk. Maybe he could finally see how horrible the world had gotten.

He was wrong.

When he greeted Asgore, he was met with nothing but coldness. Asgore told him of his plan to wage war against the Humans once they got back to the surface. Trying to make Asgore see reason… Well. It cost him his eye. The worst part was that Asgore was only lashing out. It had been an accident. Yet, he never apologized. He said nothing to Gaster even as the doctor hurried away to get treatment.

Gaster spent the night in his lab, where the little soulling sat. They were growing at an alarming rate, which worried him. He didn’t want them to grow up so quickly only to die before they got to live. But, the rate slowed as time passed. Either way, by the time the end of the week arrived with Alphys knocking on his door to tell him to eat, he was holding a little bundle of bones. They cooed up at him with so much love and sheer happiness. Gaster cried.

The baby had lovely blue magic, unstained by any sin. It was so pretty to see that Gaster couldn’t tear his eyes away. Their skull was rounded and soft, looking much like Gaster’s father in many ways. And they were healthy! They were so healthy! Fifty HoPe even for his weak stats! He gently cuddled the babybones to him, loving them with everything he had.

Gaster and Alphys both cooed over the child. She had been surprised initially when she found him crying over this child, but she could understand his happiness. It had been a major breakthrough in the science they knew. They finally managed to peel themselves off the floor when the baby started crying. It took what felt like forever for Gaster to go get some baby formula him.

Though, he did run into trouble when he got there. Being cooped up in the lab for so long, he didn’t realize how terrible the streets had gotten. He nearly lost a tooth just waiting in line at the store. He got another nasty crack in his skull to deal with though.

Being a father was a lot more difficult than he first thought. He couldn’t turn to Asgore for help. He turned to others. He found some very helpful people in Snowdin. They weren’t too far gone yet. The bunny monsters helped him, as well as the lone elemental there that was just setting up his shop.

His son, Sans, was very cute. He loved all sorts of things. He was always curious and thinking. He loved to listen to what his father was doing and liked to help out when he could. He celebrated Sans’s birthday with him every year. He got him a telescope and a couple of joke books he found in the junkyard. (He almost had to fight someone for the parts he needed. Asgore was still his employer and needed constant research updates as well.)

Despite the stress, he was liking being a father.

Sans was about six when he asked Gaster for a sibling. He… He was hesitant. Sans had left his non-dominant hand maimed. He thought about it for a month before he finally agreed. He would use his magic to work, instead of his hands. He practiced with his magic for another month, trying to gain more control and accuracy. He was going to get this right.

When it came down to it, he reluctantly recorded when he did, in case one day Sans or their sibling wanted a family. He had Alphys watch Sans until he was done healing himself.

There were some complications. He injured his other hand further than he should have. Now, he had constant stinging pain in his dominant hand. It was worth it to see yet another little soulling growing. They were smaller than Sans and they occasionally destabilized but would come back. He stayed up most nights to make sure he didn’t lose them, terrified out of his mind that he might. Sans’s growth was a cakewalk compared to this…

He tried everything in his power to not let Sans worry about them. When their bones started growing, to be very visible, he picked Sans up out of his bed and brought him to the lab.

“wha we doin’?” Sans asked, ever so soft spoken.

“I want you to see somethin’, Sansy,” Gaster said. Sans smiled brightly, clinging tightly to his blankey. When the elevator stopped, Gaster brought him to the main tube and sat down in a chair. Sans’s eyelights met the little light in the tube and just seemed to shine brighter. He looked so fascinated. He put his little hands on the glass, Gaster helping to balance him. “Careful, Sansy… This is your sibling.”

“wha’s wrong with him?” Sans asked little worry etched into his face. Gaster wasn’t going to correct him on the little slip. They didn’t know their gender yet.

“I am not quite sure. However, they are weak. They will not likely be as strong as you are, so I need you to make me a small promise.”

“yes, sir,” Sans said without hesitation.

“If I am for some reason never around, I want you to watch over them. I want you to be the best big brother you can be and protect them because they are going to need you one day.” Sans stared intently at the little tube, while Gaster hugged Sans to his chest.

“i promise.”

 

* * *

 

 

Gaster was in tears again. It wasn’t looking good for his second son. Papyrus looked so small and frail. He was afraid to touch Papyrus. His health was small, sitting at only five HP. His soul mourned for his child before they were even gone. He knew… He hated that he knew, but he did. The moment he took Papyrus out of the tube, he was not going to make it.

His eyes sockets had yet to even open, denying Gaster the chance to see his magic. ~~Denying him the chance to torture himself more, because this was his fault, all his fault for fucking.~~

Papyrus had several problems. He would stop breathing occasionally, his soul would dim dangerously, and his bones were fragile, almost like paper. He was fighting. He was such a fighter, and that’s what really killed him. Gaster knew that if Papyrus was going to live, Papyrus would have to be the one to fight. He was strong in his own way, making Gaster proud.

“daddy?” Gaster flinched, turned away from the table that had Papyrus on it. Sans stood in the doorway, curiosity etched into his face.

“Sans, what are you doing out of bed?” he asked, trying to wipe away his tears as discreetly as possible.

“wasn’t sleepy,” Sans said. “Is that him?”

Gaster was torn. He didn’t want Sans to witness Papyrus dusting, because he looked like he was about to go any minute. Gaster’s instincts to protect his boys screamed, making more tears spill. He wanted to protect Sans, but he knew hiding the truth would hurt him in the long run.

“Yes. It’s him. Would you like to come meet him?” Gaster asked, one arm stretched out in invitation. Sans nodded and strode over, his bones clicking loudly against the tile. He crawled up into Gaster’s lap and peered at the small bundle of bones.

“he’s so small.”

“Yes, he is.”

“was I ever that small?”

“No…” Gaster choked a little, hiding it behind his smile. He needed to keep this a happy moment for Sans.

“why is he so small?”

“He’s very weak, Sans. Be very careful when touching him, like when you were petting that small bird we found,” Gaster said. Sans nodded, a serious look on his face as he gently pet Papyrus’s sternum. Gaster choked back another sob when he saw Papyrus’s move slightly when the motion. Sans made to touch him lighter. Papyrus was so small. Sans would likely be able to hold him with one hand.

“i love him,” Sans stated.

“I do too,” Gaster said. “Hopefully, he will live. If he survives tonight Sans, then his chances are better than I hoped.” Sans nodded again, understanding.

“i wanna check him.”

“Okay…” Gaster said. He got out of the chair, standing Sans on it instead. He knelt down on one knee and started instruction. “First you need to pull him into an encounter. It’s simple, just concentrate on him. Good. Now, never choose ‘Fight’ when you are in an encounter with your brother. Fighting never ends happily. Press the ‘Act’ button and press check.”

Sans followed his instructions to the letter.

**Papyrus**

**LV 0**

**HP 4/4**

**ATK 0**

**DEF 1**

***He is getting really tired…**

“oh…” Sans said.

“Oh, my stars…” Gaster began to panic. His HP went down. It was the first sign of Falling. Gaster stood up quickly. “Sans keep checking him and tell me if anything changes. I have to do something.”

“yes, sir,” Sans replied. Gaster took his eyes off Sans and Papyrus and went searching through his supplies. He needed to hook Papyrus up to some monitors _now._ Perhaps he could slow this down. Do something? Anything? It was futile, and he knew it, but setting his mind to something else was helping distract him. He was hooking up the soul monitor, choking back the heavy sobs, his frame wracking him hard. Tears blurred his vision and his hands shook too much.

He shuddered so hard he had to stop what he was doing. He was going to lose Papyrus. He was going to lose Papyrus and he needed to get Sans out of there before he saw it.

“Sans, I need you to leave now. I’m going to try to help your brother,” Gaster ordered, his voice strained. Sans didn’t respond. Furrowing his brow, he turned around to look at Sans. Sans always responded in some way but –

He froze.

A bright light emitted from where Sans held Papyrus’s tiny body, one hand over his tiny, tiny soul. Sans was smiling down at Papyrus, looking more and more tired as the seconds ticked by. Wrong screamed through every part of Gaster as he watched the scene. It took him one minute and twenty-three seconds to kick back into himself. He entered the encounter immediately and checked them both.

**Papyrus**

**LV 0**

**HP 25/25**

**ATK 5**

**DEF 5**

***He loves Sans so much.**

**//**

**Sans**

**LV 1**

**HP 35/35**

**ATK 7**

**DEF 8**

***He wants to save Papyrus.**

He checked him again and to his horror, Sans wasn’t stopping.

“Sans, stop! You have to stop, you’re hurting yourself,” Gaster tried to reason. They fell on deaf ears as Sans kept transferring his HoPe to Papyrus. “Sans! Please! I don’t want to lose you! Stop!”

Gaster counted the seconds away, checking them constantly. Sans wasn’t going to stop, watching Papyrus with nothing but love as his HP rose, his bones looked a little stronger. Sans only stopped when Papyrus’s little sockets fluttered open. The encounter ended, leaving Sans only 5 HoPe and Papyrus with 55 Hope.

Gaster scooped them both up in his arms instantly, Sans’s breathing was labored, barely paying attention to his father as he fussed over them both. Gaster stopped his fussing when he heard a loud, happy squeal from the little bundle of bones. Bright green eyes stared up at them, shining brightly. Gaster found himself crying yet again and sobbing from worry, relief, and happiness when he sees Sans look up him with a sleepy look.

Without much worry, he hugs them both tightly before he went about checking Sans’s vitals. Even later, when Sans was receiving a transfusion of magic, he was petting, playing, and feeding Papyrus who now seemed to have boundless energy.

 

* * *

 

 

Papyrus was, in every sense of the phrase, a kind soul. He met everyone with a bright smile and a sweet demeanor. Even when the King stormed in the room, he paused when he came across Papyrus. Gaster had to come up with a lie, stating that a skeleton woman had come in for care and died giving birth to Papyrus, leaving Gaster with him. Asgore bought into the lie without hesitation.

Gaster noticed how Asgore’s gaze actually softened when Papyrus offered him some water.

Papyrus was about six when he made a friend. Sans was still looking after him. He was significantly weaker, sickly on occasion. In spite of his HP, he had extensive magical reserves. Sans was getting out of stripes soon, meaning he could officially help Gaster with his projects if he wanted. He was bright and smart. Papyrus was witty and just had a way of making him smile.

He never got to enjoy it.

He didn’t get to see them grow up more than that.

His had been run ragged and hadn’t been paying attention to the machine. He didn’t read the warnings in time. He had just managed to use his magic to shove Sans out the door when the explosion hit. The force sent him spiraling into the Core. He was left there, with voices, hints of others that were just like him. He met others like himself. He met himself.

For what felt like an eternity, he laid in the void, filled with regret and clinging to the love he held for his children. He regretted not doing more for them. He regretted letting the King get away with his atrocities. He held so much regret for not doing more for the people.

But, he never regretted his children.

 

* * *

 

 

He was thinking of his boys again when it happened.

He felt a pull, a tug and then horrible pain inside his head and the feeling of cramping and –

**_ “What is going on?” _ **

**Author's Note:**

> I hope you guys enjoyed the story! There will be more to come. Please let me know what you think of the story in the comments below!


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